Method to prepare the production of structured metal coatings using proteins

ABSTRACT

The invention relates to the production of thin metal layers and structures thereof on substrates of various structures. The lateral extent of a metal layer on the respective substrate can be prescribed with a precision in the micron and submicron range. The method described makes it possible to manufacture flat and three-dimensional metal structures on smooth planar or curved surfaces, as are required, for example, for depicting writing or drawings. The method uses no printing techniques.

The invention relates to the production of thin metal layers andstructures on substrate supports having a planar or three-dimensionalstructure, as are required, for example, for depicting writing ordrawings. The method avoids printing techniques.

The field of application of the invention described is the production offinely structured elements on decorative films or other thin or thickmaterials which may be flexible or rigid at room temperature. Suchmaterials provided with thin metal layers are customarily used aspackaging material or for other decorative purposes, as advertisingmaterials, in optical signal and information processing or insemiconductors technology and microelectronics as conductor plates andIC chip material or for recircuiting, e.g. on semiconductor substrates.

PRIOR ART, DISADVANTAGES OF THE PRIOR ART

Known methods and processes for producing such metallic structures onthe materials mentioned can be classified roughly into two basic types.The classification into direct and indirect methods employed here isbased on the first electrically conductive layer which is structured orapplied in structured form on a substrate having a significantly lowerconductivity. The known methods work either directly and subtractively(e.g. laser-induced ablation), directly and additively (chemicaldeposition from the gas phase—CVD, including laser-induced) orindirectly using a complicated combination of different process stepsfrom the range of microlitho-graphic structuring methods (e.g. etchingprocesses in the aqueous or gas phase). These methods are widely used insemiconductor technology.

Those techniques which utilize only a few process steps start out from aclosed metal layer or a closed metal film on the respective substrate.These can be, for example, layers obtained by lamination in the case ofthick layers (>5 μm) or layers produced by chemical and physicalgas-phase deposition methods or combinations thereof in the case of thinlayers. The latter methods typically require vacuum conditions and highvoltages or chemically aggressive gases and reagents.

Starting from a closed metal covering as is always produced, the areaswhich are required and are therefore to be retained (structuralelements) are covered with a protective layer and the part correspondingto the negative of the desired image is removed by etching. (Cf.: Menz,W.; Bley, P. (1993) Mikrosystem-technik für Ingenieure, Weinheim, NewYork, Basel, Cambridge: VCH). Relatively coarse structures can beobtained by simple cutting or stamping from a metal foil and adhesivelybonded to the appropriate surface.

Likewise, again starting from a closed metallic layer, the negativeimage can be masked with opaque lacquer or paint or a masking layer canbe applied by lamination, overprinting, adhesive bonding or in anotherway, leaving the image elements clearly exposed as shiny metallic areas.The latter technique restricts the usability of the patterns andstructures produced solely for decoration and packaging purposes.

The industrially usable production of complex metallic structures in themicron and submicron range by means of a direct lamination or sputteringprocess is not known. However, highly resolved, planar and alsothree-dimensional metallic structures can be produced on variousmaterials by means of laser-induced chemical deposition (laser-assisteddeposition—LAD, synonymously chemical vapor deposition—CVD).

However, these methods are, as mentioned above, tied to particularpressure or atmospheric conditions and can be used only for themanufacture of small batches down to a batch size of 1.

It is also possible to use combined methods. These are either printingmethods, for example screen printing techniques, in which anauxiliary-containing metal paste is applied to the material and is thenfixed to the substrate surface by remelting at elevated temperature(from about 200 to above 800 degrees Celsius). The resolution (smalleststructure width) of such processes and thus the quality of the imagesobtained is limited. The relatively high temperature required for theremelting step for pastes for producing durable metallizations restrictsthe range of materials which can be utilized here to appropriatelystable materials such as ceramics and glasses.

Printing and reproduction techniques using printing plates have, in theform of the LIGA technique, successfully found a place in the range ofmicrostructuring methods (Becker, E. W. et al., MicroelectronicEngineering 4: 35-56 (1986)). Here they are part of a complex sequenceof individual steps. Due to the plate materials employed, their maximumlateral resolution is likewise restricted to structure widths in the μmrange.

A method employing printing from plates has been described byHockberger's research group for finely structured biomolecule depositionon glass surfaces for the purpose of redirecting cell growth (Soekarno,A. et al., Neuroimage, 1, 129-144 (1994); Lom, B. et al., J.Neuroscience Methods, 50, 385-397 (1993)). A microlitho-graphicallyproduced plate enables chemical surface modifications having a lateralresolution in the μm range to be carried out.

Pritchard et al. (Angew. Chemie, 107, 84-86 (1995)) achieved proteinstrip widths of 1.5 μm on an SiO₂ surface using a mask-aidedphotochemical activation process.

The deposition of inorganic molecules and their ordered arrangement incrystalline form is a principle which has already been used in biologyby “primitive” microorganisms. Higher life forms employ the sameprinciple to provide themselves with a protective shell, a supportingskeleton or even teeth. The use of these principles for industrialapplications is being stimulated by, inter alia, Mann et al., (Science261, 1286-1292 (1993)). These authors likewise present a method ofenriching ferritin monolayers with iron oxide. However, the knownmethods have hitherto not led to crystallization of metals at localizeddeposition sites determined by proteins.

Metallization of supramolecular lipid structures is also known. It wasfound to be possible to metallize the surfaces of helicalsuper-structures (Schnur, J. M., Science 262, 1669-1676 (1993)).

It is an object of the present invention to provide a method in which,to produce laterally very finely structurable, metallic layers on anymaterials having a flat or three-dimensional surface, the necessarymetallic, previously reduced or reducible material can be applied in atargeted way with very high accuracy to the site of deposition. Thismethod should preferably do without the use of environmentally harmfulcomponents.

This object is achieved by applying a layer consisting of or comprisingproteins to the substrate to be coated, wherein under illumination(action of light) in an appropriate environment the protein or proteinsof the layer build up (form) a vectorial gradient of a physical orchemical property between two compartments formed by the layer and thechange in the physical or chemical property effected in this way in oneof the two compartments results in metal ions being reduced to metal orbeing accessible to a future reduction, after which the substrateprovided with the protein-containing layer is illuminated at thoseplaces where the metal is to be deposited (positive illumination), orsaid change in the property results in a metal deposit already presentbeing removed (etched away) at the illuminated areas of the layer(negative illumination).

The subclaims relate to preferred embodiments of the invention.

The proteins used according to the invention are ones which can act as a“pump” for the formation of a gradient of a physical or chemicalproperty directed counter to the equilibrium which is normallyestablished. The “property” can be of a physical nature, e.g. anelectron gradient, but it is preferably of a chemical nature. Examplesof chemical gradients are pH or ion (cation or anion) gradients. Theproteins can be natural proteins, proteins derived from natural proteins(e.g. gene-modified or chemically modified proteins) or syntheticproteins.

The formation of the concentration gradient should be able to be inducedby means of light (photons). Examples of such proteins occur naturally.Bacteriorhodopsin is a molecule which acts as a “proton pump” under theaction of light while an example of an anion pump is halorhodopsin (seeOesterheld, D., Israel J. of Chemistry 1995, 35: 475-494). Such proteinsare generally referred to as “retinal proteins”. They utilize, inprinciple, a cis-trans transition of a chromophore caused by absorptionof light, as has been found in the case of alkenals such as the retinalof rhodopsin (visual purple of mammals) or the retinal ofbacteriorhodopsin. Some “retinal proteins” utilize the energy gained togenerate a concentration gradient, e.g. the above mentionedbacteriorhodopsin and halorhodopsin.

As mentioned above, the proteins to be used according to the inventioncan be gene-modified proteins derived from natural proteins. Smallchanges in the structure of the amino acid chain of the protein cansometimes effect a considerable change in function: for example, amutant bacterium which produces a bacteriorhodopsin which is changed byonly one amino acid and transports chloride ions is known (Sasahi etal., Science (1995), 269: 73-75).

To obtain the necessary compartmentalization of the environment of theprotein, it is necessary either for a closed layer of protein to bedeposited on the substrate or for a closed layer of a support materialin which the protein molecules are embedded to be deposited. Sincemolecular pumps consisting of proteins usually also have to be effectiveat phase boundaries in nature and these usually consist of membranes, itis advantageous to use lipids as support material. Theprotein-containing layer therefore preferably comprises a mixture oflipids and proteins. The selection of the lipids is subject to norestrictions in principle; preference is given to phospholipids. Forcost reasons, materials such as soybean lecithin or azolecitin areadvantageously used. Of course, all phosphatidylcholines and theirderivatives are suitable in principle.

The lipids can be deposited on the substrate as a two-dimensional layerin which the protein (or various types of protein) is embedded. Anadvantage of using lipids is their three-dimensional compositioncomprising a hydrophilic head and a hydrophobic tail, as a result ofwhich the lipids arrange themselves in a parallel way (head-head andtail-tail). The protein, e.g. bacteriorhodopsin, will arrange itselfwith a preferred direction in such a layer. To maintain the action ofthe molecular pump even in the macro range, it is of course absolutelynecessary for more than half of the molecular pumps to act in onedirection. A stochastic distribution would lead to elimination of theeffect.

It is particularly preferred for the protein-containing layer to consistof or comprise lipid vesicles (liposomes) in which the protein isembedded. Here, the compartments between which the gradient is formedare the outer surroundings of the vesicle and its interior. Ifbacteriorhodopsin is incorporated into the vesicle, it arranges itselfin the artificial membrane in such a way that the pumping function can,unlike the situation in nature, also operate “inside-out”. In this way,metal ions either in the immediate vicinity of the vesicle or in itsinterior can in each case be reduced or changed in such a way that theyare accessible to reduction. The result is the localized, defineddeposition of these metal atoms. In place of reduction of the metal ions(direct reduction or change in the metal-containing molecule, e.g. anorganometallic complex, so that it becomes available to reduction), itis also possible to employ other routes which are customary in metaldeposition technology, e.g. sensitization (example: tin(II) chloride isconverted into tin(II) hydroxide which is oxidized in a palladium(II)salt bath so as to precipitate palladium metal).

If the proton pump or other chemical pump acts in the opposite direction(e.g. by lowering the pH), its illumination will lead to the reverseeffect. For this reason, such arrangements are suitable for the etchingaway of existing metal layers on the substrate. Instead of directetching, it is also possible, in this variant, to activate a metallic ornonmetallic auxiliary, e.g. a different alkali- or acid-unstablecompound, which then in turn effects etching.

The protein molecules have to remain fixed in position from the time ofillumination. This can be ensured by embedding them in the layer appliedto the substrate. In a particularly preferred embodiment, the proteinsadditionally possess an “anchor”, i.e. they are held on the substrate bymeans of van der Waals or other forces, e.g. chemical forces.

The layer consisting of or comprising proteins has to be arranged in anenvironment which allows the formation of a concentration gradient.Thus, when using a proton pump it is necessary for a sufficient numberof water molecules to be present in both compartments. Preferably, anaqueous solution in which the metal ions are present in the form of ametal salt is located within the vesicles or below the two-dimensionallayer (“two-dimensional” here refers to a layer which consists solely ofessentially adjacent particles but can be configured either as a singlelayer or as a multilayer). The outside of the vesicles (or the side ofthe two-dimensional layer facing away from the substrate) shouldlikewise be covered by an aqueous solution in which the appropriatemetal ions can be present. It is sufficient for a thin layer of thissolution to cover the vesicles, which can be achieved, if desired, bymeans of a “humid chamber”.

If vesicles are used, the local concentration gradient as describedabove either in the interior of the vesicles or on their outsidesdepending on the selected conditions may be suitable for effecting orpreparing for the reduction or etching away. If the former is the case,the vesicles naturally have to be destroyed or opened for the desiredeffect to be achieved. This can be done by means of customary methods,including the removal of the lipids and proteins.

The metal ions which can be used according to the invention may beselected as a function of the material to be deposited. Preference isgiven to selecting tin or transition metals which can, for example, becomplexed. Apart from inorganic complexes, it is also possible to useorganometallic compounds. Protonation of such compounds leads to freeradicals which decompose to metal or metal oxide. Such free radicals maybe hydrolyzed relatively slowly, i.e. may be relatively long-lived.Otherwise, or in addition, they can be stabilized, e.g. by packing themin micelles.

According to the invention, it is also possible to increase theviscosity of the metal ion solution. This measure can contribute tokeeping the proteins in fixed positions. The viscosity can be increasedby customary means, e.g. by addition of polyvinylpyrrolidone orpolyvinyl alcohol.

The surface of the substrate can be electrically conductive ornonconductive; the effectiveness of metal deposition or etching isindependent of this.

The deposition of metal which prepares for the production of structuredmetal layers does not have to form a deposit which covers the surface.It is sufficient to deposit crystal nuclei of the metal on the substratesurface. This enables highly precise deposition boundaries to beachieved (in the region of the wavelength of the light used). Thecrystal nuclei can be catalytically active in the deposition of furthermaterial in subsequent steps.

Furthermore, the method of the invention makes it possible to obtainthree-dimensional structures of the metal to be deposited.

Thus, in the method of the invention, a homogeneously covered substratesurface is used as the starting point and is covered with alight-sensitive protein layer as described above, after which thedesired pattern to be reproduced or the desired structure iswritten/drawn on by means of appropriate illumination, if desired usinga focused light source, or projected using a suitable photomask.

The method of the invention can in many cases be carried out at roomtemperature. If naturally occurring proteins are used, preference isgiven to employing a temperature which corresponds to that of thenatural environment of the protein.

In the subsequent step of a specific embodiment of the invention, whichmay, if desired, be carried out only after intermediate storage of theprepared (illuminated) materials, a metallic layer is deposited from aliquid phase at the places on the material which have been changed byillumination (image elements). After appropriate intermediate steps foravoiding undesired deposition of the layer at unintended places on thesubstrate—to increase contrast—this layer is used for furthermetallization.

The method of metallization using molecules whose optical properties canbe changed or complex mixtures of such molecules is also suitable forproducing three-dimensional structures. These structures, which can beregarded as comprising a plurality of individual layers joined to oneanother in a complex fashion or constituents of such layers can beproduced by targeted irradiation with focused light at the appropriateplaces for metal deposition in a three-dimensional substrate which maybe homogeneous or inhomogeneous in terms of its material compositionand/or structure. Such a substrate can be, for example, a sol, a gel, aglass or a monolithic or porous solid, for example a crystal compactsimilar to a sugar cube. From a complex, three-dimensional layerstructure formed in the described sense, the underlying substrate whosesurface has been utilized for deposition of the layer can be removedagain either completely or partially (e.g. by dissolution in a suitablesolvent). This leaves, in the case of the simple removal of a planarsubstrate, a finely structured planar layer of the deposited material,or else a complex, three-dimensional structure. This structure thenconsists of a metallic material or a material comprising a metalliccomponent.

In each case, in this embodiment of the invention, a layer of moleculesand possibly auxiliaries is present on the surface of or in thesubstrate and this layer leads, by means of a light-addressed change inthe properties of a significant constituent of the layer, to formationof areas of preferred metal deposition during the course of subsequentprocesses.

A further embodiment of the invention exploits the particular propertiesof a substance which acts as a molecular pump, for example thebacteriorhodopsin molecule which can be isolated from bacterial biomass.The targeted deposition of a monolayer of such molecules is hereutilized for highly resolved local corrosion or modification of thesubstrate underneath in a liquid medium. The molecule referred to as a“pump” has the ability to transport substances, for example protons (H⁺)or ions, selectively under the action of light from the solution side tothe substrate side through a layer which serves simultaneously assupport and barrier. By means of these factors attained in the immediatevicinity of the substrate surface, a structuring of the substratesurface is carried out. The structuring can lead only to creation ofotherwise undetectable defect sites. In a subsequent step, which iscarried out only after removal of the layer containing “pumps” whichhave been partially activated optically, a further structuring or otheralteration of the material is carried out. This can be isotropic oranisotropic etching or the formation of a layer, for example bycrystallization of a substance which then comes into contact with thesubstrate from a solution, a suspension or a gas.

Advantages of the method of the invention can be summarized as follows:the locally highly resolved deposition of the primary metallic layerwhich is later catalytically active or directly active ascrystallization nucleus at the location of molecules which have beenaltered beforehand by optical means allows precision in the region ofthe wavelength of the light used, but at least, if appropriate, in theregion of the vesicle size. The use of focused light, for instance thatof a laser beam, and the simplicity of the procedure allowsmetallization to be carried out both in and under porous layers. Here,identical or different planar metallizations superposed in a pluralityof layers can be electrically connected via predetermined bridges.Combining suitable parameters makes it possible to build up planar andthree-dimensional structures comprising two or more different metals.Such complex metallization structures can be used as high-densityrecircuiting structures. Method-determining parameters are given by theoptical absorption properties of various proteins or otherlight-sensitive substances mixed with them, and/or the timedelayedincubation with solutions of different metals, or the controlledreaction kinetics in complex solutions and mixtures. The lateral extentof a metallic layer on the respective substrate can be predeterminedwith a precision in the micron and submicron range. The method describedmakes it possible to produce flat and three-dimensional metal structureson smooth, planar or curved, electrically conductive or nonconductivesurfaces.

The latter preferred embodiment of the method of the invention(production of structured materials or layers) is based on the sameprinciple of the optically addressable targeted modification of a layersuitable for this purpose on a surface.

The method of the invention makes it possible to achieve, for example, adecorative, shiny metal layer for writing on surfaces.

The abovementioned embodiments of the invention can be utilized forbuilding up complex layers and structures. Here, the material whichfinally dominates the structure produced can have a different materialcomposition than the underlying substrate surface or the substrateitself.

The metals or metal ions which can be used according to the inventioncan be selected from among tin and the group consisting of transitionmetals or transition metal ions, in particular from among tin, iron,chromium, rhodium, nickel, palladium, platinum, iridium, gold and/orrhenium. The metal ions can be in the form of inorganic compounds, e.g.as protonatable organometallic compounds of nickel, palladium and/orplatinum.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures illustrate the inprinciple proceduresdescribed. In the figures:

FIG. 1 shows the sequence of steps of a photo-addressed metallization,

FIG. 2 illustrates the precision of the deposition of the layer and

FIG. 3 shows the sequence of steps of a fine etching technique aided bya “molecular pump”.

In FIG. 1, the reference numeral 1 denotes a supporting/fixing auxiliary(e.g. lipid), 2 denotes a photoactive molecule, such a moleculecomposite or cluster, 3 denotes the substrate; 4 representscrystallization nuclei and 5 represents a deposited metal layer. Thesequence of steps shows, from the top down, the substrate 3 alone, thesubstrate with deposited layer of photoactivatable molecules in asupporting matrix, the selective illumination (hν) of a photoactivatablemolecule or molecule composite (dry or wet), the primary metallizationeffected thereby to form crystallization nuclei and, in the bottom row,the secondary metal deposition.

FIG. 3 shows, likewise from the top down, the etching procedure, wherethe substrate (drawn in as a broken line) with a metal layer depositedthereon (“primary layer”) drawn in as a continuous, thicker black line)is coated in the second row with monolayers of photoactivatablemolecules in a support (support function). Selective illuminationinduces local pH gradients, recognizable by defects in the metal layerwhich are enlarged by biomimetic corrosion (4th row). Removal of thephotoactivatable molecules stops the corrosion (last row).

The invention is illustrated below by means of examples.

1. General

Liposomes containing stabilized metal ions in solution in the enclosed,internal liquid pool and bacteriorhodopsin molecules (BR) oriented in apreferred direction (vectorially) in their lipid membrane are prepared.A dispersion of such liposomes is applied as a closed, thin layer to thesubstrate to be provided with a metal structure and is partlyilluminated with the aid of an appropriate photomask. At the placeswhich are illuminated, the pH of the liquid encapsulated in theliposomes changes as a result of the activity of the molecular protonpump BR. The shifts over time of the pH triggered in this way areutilized for modifying the solution of the encapsulated metal salt.Depending on the type of complexes, metal salts can be destabilized andpartially or completely altered in this way. The associatedmodifications of the liposome contents are utilized in subsequent stepsto partly activate the substrate by customary methods of chemical(=autocatalytic=electroless) metallization. This activation comprisesthe deposition of metal nuclei. Such metal nuclei are then utilized, bymeans of customary methods of chemical or electrochemical metallization,for producing electrically conductive structures, including structuresof metals other than that of the salts and/or complexes used initially.

The principle described, namely optically manipulating components ofknown activation or metallization baths encapsulated in liposomes bymeans of light-driven molecular proton pumps so as to lead to partialchemical contrasts which correspond to the optical contrasts utilizedfor manipulation, can, depending on the components used and theirorientation in the liposome membrane (e.g. BR), give both negative andpositive images of the illumination patterns.

2. Typically, the Following Working Steps can be used

The amount of lipid required for the preparation of a 0.1-0.5% strengthlipid suspension is weighed into a test tube and, together with a 0.01-1mM solution of a salt or complex of a metal (for example 100 μMpalladium(II) chloride), suspended by customary methods with the aid ofan ultrasound generator in a 0.01-5 M salt solution of a chloride,sulfate, carbonate, nitrate or phosphate whose pH can be set to valuesaround or below pH 8 (for example 0.5 M potassium sulfate). Whilecooling constantly in a (tap water) cooling bath, a clear, slightlyopalescent liposome dispersion can be obtained within about 10 minutes,depending on the power used. The prepared liposome dispersion is addedto a solution of the BR (bacteriorhodopsin) intended for reconstitutionin the liposome membrane. The “incorporation” of the BR into theliposomes is again carried out by means of a titanium probe of anultrasound generator over a period of about 3 minutes, but can also becarried out in another way, as customarily employed in various variantsin biochemistry, biophysics or medicine. To evaluate the (orientedreconstitution of the BR in the) BR-metal salt-liposome preparationobtained, an aliquot is irradiated with yellow light (1>500 nm) in aglass cell while mixing continuously. The effective preferentialorientation of the BR molecules in the vesicle membrane and the pumpingrate achieved are concluded from the readily measured change in the pHin the external volume (combination pH electrode). Suitable preparationsare ones which induce pH changes of about 0.1 pH units underillumination.

To increase the viscosity of the dispersion, it is possible to addpolymers, for example polyvinyl-pyrrolidone (PVP) or polyvinyl alcohol(PVA). It is thus possible to apply, for example, a 7.5% strengthPVPliposome dispersion as a thin film to the substrate, for exampleusing a spin coater customary in microelectronics technologies. Thesubstrate which has been prepared in this way is then illuminatedthrough the photomask with yellow light (1>500 nm) in a humid atmosphere(“humid chamber”). The illuminated substrate is then dried in a hot airoven and is then available for conventional chemical metallization, forexample with a nickel-boron layer (NiB).

3. Example

5 mg of azolectin (Sigma-Aldrich) are sonicated for 15 minutes in 5 mlof an aqueous 100 μM tetrammine palladate solution in 0.5 M potassiumsulfate in a test tube using the titanium probe of an ultrasoundgenerator (Branson Sonifier W 450). The clear, slightly opalescentdispersion is admixed with a bacteriorhodopsin solution in a molar ratioof lipid:protein of 700:1 and sonicated for a further 3 minutes whileavoiding strong cavitation. Polyvinylpyrrolidone (molecular weight about350,000-SERVA) is added to 7.5 percent by weight and completelydissolved with stirring (Vortex). This slightly syrupy solution isapplied in a thin layer to the substrate to be coated, for example aglass fiber-reinforced epoxy material (FR-4 printed circuit substratematerial). A photomask is projected by means of yellow light (Schottfilter OG 515) onto this layer using a suitable optical arrangement. Toprevent drying-out of the liposome layer, the last-named step is carriedout in an atmosphere saturated with water vapor. For this purpose, thesubstrate is present in a “humid chamber”. After illumination, thesubstrate is dried in a hot air oven. This is followed by conventionalNiB deposition.

The invention will be summarized once more below, with additional,specific embodiments being mentioned: It relates to a process forproducing structured metal layers on surfaces or their preparation, inwhich, starting from protein molecules adhering to the surface of asolid, the properties of the protein molecules are changed locally andthus are compared to the unchanged protein molecules on the layer at thesite of the deposition of metal from a solution or suspension and/or thebinding of colloidal metal particles or atomic clusters from a liquidcontaining them or a gas or a gas mixture, a protein layer orconstituents of such a layer arranged with molecular resolution servesas initiator of a reaction at a surface which is wetted by a solution oris brought into contact with a defined gas composition, a localconcentration gradient of at least one component in the liquid or thegas phase in the immediate vicinity of particular protein molecules canrepresent a significant influencing parameter for controlling thedeposition process, light of a discrete wavelength from the spectrum ofvisible light is a factor which modifies the character of the proteinmolecules adhering to the surface, the conformation of a polymericcomponent comprising various amino acid groups as structural units andlocated at the site intended for the deposition of metal represents aparameter which determines the metallization process.

Furthermore, the invention encompasses embodiments in which

structured metal layers are produced on surfaces in contact with aliquid phase, as disclosed above, where bacteriorhodopsin or aderivative thereof or a variation thereof represents the proteincomponent in the layer or is a significant constituent of the layer,

a protein mixture or a mixture of proteins with further moleculescapable of various conformations is used for forming the layer,

the layer is stabilized by a type of molecule which is chemically inertunder the further conditions,

discrete regions of the primary protein-containing layer absorb light ofdifferent wavelengths at different times or synchronously,

discrete regions of a primary nonmetallic layer are excited by light ofdefined wavelength and/or are locally changed in their properties,

the liquid phase can comprise the salt of a metal to be deposited indissolved form,

the liquid phase represents a colloid of very small (>200 nm diameter),charged particles,

the liquid phase can comprise a metal colloid,

the composition of the liquid phase changes over the duration of contactwith the substrate,

the properties of the components which lead to formation of a metallayer and are present in the liquid are stabilized by the presence ofother dissolved substances or are improved for the intended purpose ofdeposition of a layer,

the surface intended for deposition of the metal layer can be covered bya porous layer,

the surface intended for deposition of the metal layer can represent theinternal surface of a porous material,

the surface intended for deposition of the metal represents the surfaceof a material which can be shaped at room temperature or at elevatedtemperature,

the substrate which serves as a base for formation of the layer and issolid under the conditions of the deposition of the layer can be partlyor completely removed, replaced by another material or supplemented in asubsequent step without complete destruction of the metallic structurewhich has been deposited,

a laterally structured metal layer prescribes the surface arrangement ofa primary material which aids the deposition of a further metal,

the finely structured metal layer obtained serves for purposes ofconstructing a circuit and conducting electric current,

the finely structured metal layer obtained is used as graphic imageelement or text constituent,

the metal structure obtained is used for measurement or as a sensor,

the metal structure obtained is used in the field of automobile orvehicle construction, the metal structure is produced by means of amolecular pump which is activated by selective illumination or by meansof another principle which produces a local concentration gradient,

the formation of the metal layer proceeds to completion at the locationsof the previous light-activated protein molecules whose properties canbe controlled.

What is claimed is:
 1. A method of preparation for the production ofstructured metal layers on substrate surfaces, comprising the followingsteps: (a) application of a layer comprising proteins to the substratesurface, where the protein or proteins of this layer is/are selectedfrom among proteins which, under the action of light, form a cation oranion concentration gradient between two compartments formed by thelayer and the change in the ion concentration effected in this way inone of the two compartments results in metal ions or compounds presentthere being reduced to metal or being accessible to a future reduction,and (b) differential illumination of the substrate provided with theprotein-containing layer.
 2. The method according to claim 1, whereinthe cation or anion concentration gradient is a pH gradient.
 3. Themethod according to claim 1, wherein the protein-comprising layercomprises protein selected from the group consisting of retinal protein,natural bacteriorhodopsin, modified bacteriorhodopsin, naturalhalorhodopsin, and modified halorhodopsin.
 4. The method according toclaim 1, wherein the illumination is effected by means of light having adiscrete wavelength.
 5. The method according to claim 1, wherein theprotein-containing layer comprises a mixture of lipids and proteins. 6.The method according to claim 5, wherein the protein-containing layer isa two-dimensional layer of lipids with proteins present therein.
 7. Themethod according to claim 5, wherein the protein-containing layerconsists of or comprises lipid vesicles or liposomes into whose wallsproteins are incorporated.
 8. The method according to claim 1, whereinthe metal or the metal ions are selected from the group consisting of atransition metal, transition metal ion, tin, tin ion, iron, iron ion,chromium, chromium ion, rhodium, rhodium ion, nickel, nickel ion,palladium, palladium ion, platinum, platinum ion, iridium, iridium ion,gold, gold ion, rhenium, and rhenium ion.
 9. The method according toclaim 1, wherein the metal ions in the form of inorganic or organiccomplexes or of organometallic compounds.
 10. The method according toclaim 9, wherein the metal ions in the form of protonatableorganometallic compounds of nickel, palladium and/or platinum.
 11. Amethod of preparation for the production of structured metal layers onsubstrate surfaces, comprising the following steps: (a) application of alayer comprising proteins to a substrate surface coated with metal,where the protein or proteins of this layer is/are selected from amongproteins which, under the action of light, form a cation or anionconcentration gradient between two compartments formed by the layer andthe change in the ion concentration effected in this way in one of thetwo compartments results in the metal being oxidized from the coatingand being brought into solution, and (b) differential illumination ofthe substrate provided with the protein-containing layer.
 12. The methodaccording to claim 11, wherein the cation or anion concentrationgradient is a pH gradient.
 13. The method according to claim 11, whereinthe protein-containing layer comprises a protein selected from the groupconsisting of retinal protein, natural bacteriorhodopsin, modifiedbacteriorhodopsin, natural halorholopsin, and modified halorholopsin.14. The method according to claim 11, wherein the illumination iseffected by means of light having a discrete wavelength.
 15. The methodaccording to claims 11, wherein the protein-containing layer comprises amixture of lipids and proteins.
 16. The method according to claim 15,wherein the protein-containing layer is a two-dimensional layer oflipids with proteins present therein.
 17. The method according to claim15, wherein the protein-containing layer comprises lipid vesicles orliposomes into whose walls proteins are incorporated.
 18. The methodaccording to claim 11, wherein the metal or the metal ions are selectedfrom the group consisting of transition metal, transition metal ion,tin, tin ion, iron, iron ion, chromium, chromium ion, rhodium, rhodiumion, nickel, nickel ion, palladium, palladium ion, platinum, platinumion, iridium, iridium ion, gold, gold ion, rhenium, and rhenium ion. 19.The method according to claim 11, wherein the metal ions are in the formof inorganic or organic complexes or of organometallic compounds. 20.The method according to claim 19, wherein the metal ions are in the formof protonatable organometallic compounds of nickel, palladium and/orplatinum.